Hydraulic Steering System For Forklift Trucks

ABSTRACT

A hydraulic steering actuator system for a forklift with front and rear sections includes a hydraulic steering motor. The forklift front section includes a mast mounting a pair of fork blades and a pair of wheels. The forklift rear section mounts a pair of drive wheels. The forklift front and rear sections are connected by an articulated connection with a vertical rotational axis. The steering actuator motor driveshaft extends generally along the vertical rotational axis. First and second actuator mounting brackets are connected to the forklift front and rear sections respectively. One of the mounting brackets includes upper and lower locking assemblies locking the hydraulic steering motor driveshaft whereby torque applied to the steering motor is transmitted to the articulated connection for turning the forklift front section relative to the forklift rear section. The range of motion is preferably 180°-205° for accommodating sideloading operations from relatively high storage shelves, e.g. in narrow-aisle warehouses.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosed technology relates generally to a system forsteering and operating forklift trucks, and more specifically tosteering and operating a narrow-aisle, articulated forklift truck usinga hydraulic actuator.

2. Description of the Related Art

A typical narrow-aisle articulated forklift truck (or “forklift”)comprises front and rear chassis sections each having a pair of wheelson a respective common axis. The rear wheels provide drive-motion to theforklift truck, while the front wheels are non-driven and steer thetruck. The chassis sections are pivoted together about a vertical axisso that the front chassis section, including a mast, can be turned at anangle of approximately 90° each way (preferably 180°-205° total range ofmovement) relative to the rear chassis section to the allow the truck toinsert loads into, and remove loads from, the faces of the aisle.

Without limitation on the generality of useful applications of thepresent invention, an exemplary use consists of loading and unloadingpalletized inventory in narrow-aisle facilities, such as warehouses.Steering with the front wheels is generally preferred for suchapplications because rear-wheel steering forklifts generally haverelatively large turning radii and are thus ill-suited for loading andunloading storage bins in narrow aisles, such as those found in manywarehouses and other storage facilities. Narrow-aisle, articulatedforklift trucks, on the other hand, allow the mast-portion of theforklift to turn independently from the body of the truck, which allowsthe operator to load or unload material positioned perpendicular to theaisle along which the truck is traveling. Typical narrow-aisle trucksare capable of rotating the front chassis mast section at least 90° eachway relative to a direction of travel along a warehouse shelf aisle.

A problem condition associated with many previous articulated forklifttrucks is the articulating joint between the front and rear chassissections. An electric or hydraulic motor is typically used to steer theforklift truck by rotating the front chassis section relative to therear section. Because the front chassis includes the mast, which issubjected to heavy loads, the rotation motor and connection arehigh-wear components which can be expensive to replace. What is neededis an articulated forklift truck capable of maneuvering in narrow aislesand handling heavy loads while minimizing the wear on the articulatingcomponent of the truck.

Heretofore there has not been a forklift truck embodying thecapabilities of the invention presented herein.

SUMMARY OF THE INVENTION

Disclosed herein in an exemplary embodiment is a narrow-aislearticulated forklift truck including front- and rear-chassis portions. Ahydraulic actuator capable of allowing rotation through approximately180°-205° joins the two portions and is capable of absorbing thehigh-wear forces of loads applied to the front-chassis portion.

The hydraulic actuator provides a connection between the front and rearchassis portions, allows the front-chassis portion to rotate about theactuator, and provides a means for hydraulic power to pass through theactuator to the forklift truck mast, allowing the mast to tilt and thefork to raise and lower while protecting the hydraulic hoses.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constitute a part of this specification and includeexemplary embodiments of the disclosed subject matter illustratingvarious objects and features thereof, wherein like references aregenerally numbered alike in the several views.

FIG. 1 is an isometric view of an articulated forklift with a hydraulicsteering actuator comprising a preferred embodiment of the presentinvention.

FIG. 2 is a side elevational view of the preferred embodiment of thepresent invention.

FIG. 3 is a top-down plan view of the preferred embodiment of thepresent invention demonstrating the rotational capabilities of thefront-chassis portion.

FIG. 4A is an isometric view of the hydraulic steering actuator.

FIG. 4B is another isometric view of the hydraulic steering actuator.

FIG. 5A is an exploded isometric view of the hydraulic steering actuatorand a mounting bracket used for connecting the actuator to thefront-chassis portion of the forklift.

FIG. 5B is another isometric view of the hydraulic actuator and themounting bracket shown in FIG. 5A.

FIG. 6 is a sectional view of the hydraulic actuator taken generally along line 6-6 in FIG. 5B.

FIG. 7 is an elevational view showing the connection of the mountingbracket and the hydraulic actuator in the direction of arrow 7 in FIG.6.

FIG. 8A is an exploded isometric view of the hydraulic actuator and themounting block used for connecting the actuator to the rear-chassisportion of the forklift.

FIG. 8B is an isometric view of the hydraulic actuator and mountingblock of FIG. 8A.

FIG. 9 is a side elevational view of the connection of the mountingblock and the hydraulic actuator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction andEnvironment

As required, detailed aspects of the disclosed subject matter aredisclosed herein; however, it is to be understood that the disclosedaspects are merely exemplary of the invention, which may be embodied invarious forms. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as abasis for the claims and as a representative basis for teaching oneskilled in the art how to variously employ the present invention invirtually any appropriately detailed structure.

Certain terminology will be used in the following description forconvenience in reference only and will not be limiting. For example, up,down, front, back, right and left refer to the invention as oriented inthe view being referred to. The words “inwardly” and “outwardly” referto directions toward and away from, respectively, the geometric centerof the embodiment being described and designated parts thereof.Forwardly and rearwardly are generally in reference to the direction oftravel, if appropriate. Said terminology will include the wordsspecifically mentioned, derivatives thereof and words of similarmeaning.

A preferred embodiment of the present invention is an articulatingforklift truck 2 comprised of a front-chassis portion 5 and arear-chassis portion 3. The forklift truck 2 is designed to operatealong narrow aisles by loading inventory or items located perpendicularto the forklift truck's path. The front-chassis portion 5 and therear-chassis portion 3 are joined at a pivot point formed by a hydraulicactuator 8 bolted to a mounting block 78 and a mounting bracket 10. Anexample of a suitable hydraulic actuator 8 includes the T20 SeriesHydraulic Actuator manufactured by Helac Corporation of Enumclaw, Wash.Such a hydraulic actuator 8 operates as a complete steering and bearingsystem in a single, rugged component. The actuator 8 is adapted forhandling the high-wear loads placed upon it when inventory is lifted bythe forklift truck 2.

II. Articulating Forklift Truck 2

Referring to the drawings in more detail, the reference numeral 2generally refers to the articulating forklift truck used for loading andunloading inventory along narrow aisles. Articulating forklift trucksare used in such circumstances because the front-chassis portion 5 ofthe forklift truck 2 is capable of rotating 90° or more to the right orthe left of the path traveled by the forklift truck. The forklift mast 6and the fork blades 4 are mounted to the front-chassis portion 5 and,when rotated, can lift or unload inventory without adjusting the travelpath of the forklift truck 2.

FIGS. 1-3 generally show an articulating forklift truck 2 in a preferredembodiment, including the front-chassis portion 5 and the rear-chassisportion 3. The rear-chassis portion 3 is further comprised of anoperator's seat 20, a roll cage 22, steering controls (steering wheel)24 and mast and fork controls 26. A mounting block 78 with upper andlower mounting flanges 80, 81 is located below the operator's seat 20and the steering controls 24. A steering and control subsystem 12, ahydraulic subsystem 13, and a computer processor 14 are mounted withinthe rear-chassis 3 for coordinating control signals from the operator tothe forklift truck 2. For example, the hydraulic steering and controlsubsystem 12 can differentially drive the rear wheels 15 for effectivelyoperating the forklift 2 in a zero turning radius (“ZTR”) mode ofoperation. Thus, the forklift front portion 5 can be advanced towards aline of shelves even when the front wheels 17 are turned at 90° rightangles to the longitudinal axis. The control subsystem 12 canautomatically meter hydraulic fluid to the steering actuator 8 andotherwise control the drive train of the forklift 2 in various operatingmodes, such as straight-line driving, turning and store-and-retrievewarehouse shelving procedures.

The front-chassis portion 5 is further comprised of a mast 6 and forks 4vertically adjustably mounted thereon. A fork cable assembly 30 ismounted atop the mast 6 and connected to the forks 4. The cable assembly30 is controlled via the fork controls 26 and is capable of raising andlowering the fork 4 along the mast 6. A mounting bracket 10 is connectedto the rear of the mast 6. Two mast tilt hydraulic cylinders 28 aremounted on either side of the mounting bracket 10 and connected to themast 6. The tilt cylinders 28 allow the mast 6 to be tilted forward orbackwards, allowing positioning of the forks 4.

A central portion 7 joins the front-chassis portion 5 to therear-chassis portion 3. The central portion 7 is comprised primarily ofa hydraulic actuator 8 bolted to the mounting block 78 and the mountingbracket 10. A sensor system 31 is attached to the mounting block 78 andthe hydraulic actuator 8 and includes a rotation sensor 16 fordetermining the rotation degree of the front-chassis portion 5 relativeto the rear-chassis portion 3, and a hydraulic sensor 18 for determiningthe tilt of the mast, along with the other hydraulic functions of theforklift truck 2.

As shown in FIG. 3, the front-chassis portion 5 is rotatable about thehydraulic actuator 8. The rotation radius R indicates the rotationalpath of the front-chassis portion 5 as it rotates about the hydraulicactuator 8. The rotation path allows for at least a 90° rotation of thefront-chassis portion 5 to either side of the forklift truck 2longitudinal axis.

FIGS. 4A and 4B show the hydraulic actuator 8 in more detail. Theactuator 8 is comprised of an actuator body 36, an actuator upper flange40, a lower flange 41, and a rotator shaft 38. Each actuator flange 40,41 includes a hydraulic inlet/outlet port 34 and a plurality of boltholes 32. The bolt holes 32 allow the actuator 8 to be physically boltedto the mounting block 78 via a plurality of mounting bolts 54.

The upper actuator flange 40 includes a first port 42, and the loweractuator flange 41 includes a second port 43. The first and second ports42, 43 include plugs which can be loosened and tightened to adjust therotation angle of the actuator. When constructing the forklift truck 2,the plugs located in the first and second ports 42, 43 are loosened. Theactuator 8 is rotated 90° so that it is perpendicular to the mountingbracket 10. The plugs located in the first and second ports 42, 43 arethen re-tightened. This allows the forklift front chassis portion 5 torotate through 180° or more for sideloading capability.

FIGS. 5A-7 show the connection of the hydraulic actuator 8 to themounting bracket 10. As shown in FIG. 5A, the mounting plate 10 isfurther comprised of a bracket plate 44 including a lower mountingprojection 60 with a lower mounting projection opening 66, a bracketbase protrusion 64 with a bracket base protrusion opening 70, fourtilt-hydraulic connection flanges 50 each including a hinge receiver 52,two recesses 46 each including two hydraulic access receivers 48, andfour bolt-holes 58. An upper mounting projection 62 includes an uppermounting projection opening 68 which receives the upper stem of thehydraulic actuator rotator shaft 38. An upper locking assembly 72secures the upper mounting projection 62 to the hydraulic actuator 8.

The upper mounting projection 62 bolts to the bracket plate 44 via fourmounting bolts 54 and associated washers 56. The lower stem of therotator shaft 38 is secured within the lower mounting projection opening66 with a lower locking assembly 74. As shown in FIG. 5B, with thehydraulic actuator 8 mounted to the mounting bracket 10, the hydraulicinlet/outlet ports 34 are accessible facing out from the bracket 10. Atilt hydraulic cylinder 28 is connected to each pair of connectorflanges 50 via a hinge connection 76.

FIGS. 8A-9 demonstrate the connection of the hydraulic actuator 8 to themounting block 78. As shown in FIG. 8A, the mounting block 78 includesan upper mounting flange 80 and a lower mounting flange 81, eachincluding a plurality of bolt holes 82 and a hydraulic port access 84.Mounting bolts 54 connect the hydraulic actuator 8 to the mounting block78 through the flange bolt holes 82 and the actuator bolt holes 32. Asensor system 31 comprising a sensor body 86 and a sensor arm 88 ismounted to the top face of the mounting block 78. The arm 88 interactswith the hydraulic actuator 8 to determine the rotation angle of theactuator 8.

As shown in FIGS. 8B and 9, hydraulic hoses 90 are fed through thehydraulic port accesses 84 and connected to the hydraulic actuator'shydraulic inlet/outlet ports 34. The hydraulic hoses 90 connect to thehydraulic subsystem 13 located in the rear-chassis portion, and travelthrough the actuator 8 to the various hydraulically powered componentslocated in the front-chassis portion 5.

III. Operation of the Hydraulic Steering Actuator 8 and the ForkliftTruck 2

In an embodiment of the present invention, an operator positioned in theoperator's seat 20 in the rear-chassis portion 3 controls the motion ofthe forklift truck 2 by powering the rear wheels 15. Using the steeringcontrols 24, the operator turns the front-chassis portion 5 by rotatingthe hydraulic actuator 8, turning the front wheels 17 and directing theforklift truck 2 in the process.

The operator also controls the tilt of the mast 6 and the lift of thefork 4 using the fork controls 26. The tilt of the mast 6 is controlledthrough the hydraulic system. The hydraulic hoses 90 connect to thehydraulic actuator 8, from which the hydraulic tilt cylinders 28 arefed. These hydraulic cylinders 28 allow the entire mast 6 and the fork 4to tilt away from or towards the rear-chassis portion 3 of the forklifttruck 2. If the operator requires the fork 4 to be maneuvered beneath apiece of inventory, the operator can tilt the mast and the fork 4forward, guide the truck toward the object, and then tilt the mast 6 andthe fork 4 backwards, resulting in the inventory object being liftedfrom the ground and onto the fork 4.

The rotator shaft 38 of the hydraulic actuator 8 is drivingly connectedto and causes the front-chassis portion 5 to rotate according to thesteering wheel movements by the operator. The upper and lower lockingassemblies 72, 74 create a rigid connection between the rotator shaft 38and the upper 62 and lower 60 mounting projections of the mountingbracket 10. An example of the locking assemblies 72, 74 is the RingfederLocking Assembly RfN 7013 manufactured by Ringfeder GMBH of Germany. Theforklift front wheels may optionally turn in the same direction as theactuator rotator shaft 38 to assist in turning the forklift truck 2.

It will be appreciated that the articulated forklift truck can be usedfor various applications not described herein. Moreover, the articulatedforklift truck can be compiled of additional elements or alternativeelements to those mentioned herein, while providing similar results.

It is to be understood that while certain aspects of the disclosedsubject matter have been shown and described, the disclosed subjectmatter is not limited thereto and encompasses various other embodimentsand aspects.

1. A steering actuator system for a forklift including a front sectionwith wheels and a mast mounting a vertically movable load connector, arear section with drive wheels and said front and rear sections beingconnected at an articulated connection with a generally verticalrotational axis, which steering actuator system comprises: a hydraulicactuator including a rotating hydraulic steering motor with a coaxialdriveshaft and a pair of hydraulic fluid ports; said hydraulic actuatorincluding upper and lower actuator flanges mounted on said hydraulicsteering motor and each including a respective hydraulic fluid port; aforklift front section mounting bracket connected to said forklift frontsection; a forklift rear section mounting bracket connected to saidforklift rear section; said actuator flanges being connected to one ofsaid front and rear section mounting brackets; and said driveshaft beingconnected to the other of said mounting brackets.
 2. The steeringactuator system according to claim 1 wherein said driveshaft isgenerally aligned with the forklift front section vertical rotationalaxis.
 3. The steering actuator system according to claim 1, whichincludes: a hydraulic piston-and-cylinder unit connected to said frontsection mounting bracket and said mast; said forklift front sectionincluding a chassis mounting said mast and said front section mountingbracket; and said piston-and-cylinder unit being adapted for tiltingsaid mast relative to said forklift front section.
 4. The steeringactuator system according to claim 1, which includes: said forklift rearsection including a steering wheel; a hydraulic system connected to saidsteering actuator and said steering wheel; and said steering wheelhydraulically controlling the rotation of said hydraulic steering motor.5. A steering actuator system for a forklift including a front sectionwith wheels and a mast mounting a vertically movable load connector, arear section with drive wheels and said front and rear sections beingconnected at an articulated connection with a generally verticalrotational axis, which steering actuator system comprises: a hydraulicactuator including a rotating hydraulic steering motor with a coaxialdriveshaft and a pair of hydraulic fluid ports; said driveshaft beinggenerally aligned with the forklift front section vertical rotationalaxis; said hydraulic actuator including upper and lower actuator flangesmounted on said hydraulic steering motor and each including a respectivehydraulic fluid port; a forklift front section mounting bracketconnected to said forklift front section; a forklift rear sectionmounting bracket connected to said forklift rear section; said actuatorflanges being connected to one of said front and rear section mountingbrackets; said driveshaft being connected to the other of said mountingbrackets; a hydraulic piston-and-cylinder unit connected to said frontsection mounting bracket and said mast; said forklift front sectionincluding a chassis mounting said mast and said front section mountingbracket; said piston-and-cylinder unit being adapted for tilting saidmast relative to said forklift front section; said forklift rear sectionincluding a steering wheel; a hydraulic system connected to saidsteering actuator and said steering wheel; and said steering wheelhydraulically controlling the rotation of said hydraulic steering motor.